This application relates to a pin for anchoring a replacement ligament inside a tunnel formed in a bone. More particularly, the present invention relates to a pin which facilitates securing a replacement ligament graft inside a bone and which promotes healing of the ligament graft inside the bone.
When a ligament such as an anterior cruciate ligament (ACL) of a knee is damaged or torn, a replacement ligament is often installed in the knee to reconstruct the natural anterior cruciate ligament. During such reconstruction, a tunnel is typically drilled through the anterior portion of the tibia upwardly through the tibial plateau and into the distal end of the femur to approximate the natural position of the anterior cruciate ligament. A bone-ligament-bone graft is then harvested, often from the patellar tendon following standard grafting procedures. Typically a wedge-shaped graft is cut and contoured using a graft guide. Sutural holes are then formed in the graft. The graft is then installed into the drill tunnel.
Various methods are known for securing the graft within the tibia and femur until the graft can heal. One such method is the use of a Kurosaka.TM. fixation screw. The Kurosaka.TM. screw provides an interference fit inside the tunnel with the graft so that the graft is wedged against the wall of the tunnel. See, for example, U.S. Pat. No. 4,950,270.
In other known methods, sutures coupled to the graft are anchored to the bone using screws or washers. The ligaments can also be coupled directly to the bone using plates or washers.
In addition, it is known to use a pin transverse to the drill tunnel to secure the graft within the tunnel. Various apparatus and methods are known for aligning the pin transverse with the drill tunnel to secure the ligament replacement to the bone. See, for example, U.S. Pat. No. 4,901,711 and U.S. Pat. No. 4,985,032.
Other methods and apparatus for locating and installing a transverse pin for securing a replacement ligament to a bone are described pending in U.S. patent application Ser. No. 08/004,987, entitled METHOD FOR SECURING A LIGAMENT REPLACEMENT IN A BONE by inventors Goble and Lower, filed concurrently herewith, and pending U.S. patent application Ser. No. 08/004958, entitled DRILL GUIDE APPARATUS by inventors Goble and Lower, also filed concurrently herewith.
The pin of the present invention provides advantages over the prior transverse pins and screws. The pin includes a smooth shank which is preferably tapered to push the bone plug of the bone graft against one side of the tunnel to promote healing of the graft in the bone. This tapered shank constitutes means for pushing or urging a portion of a ligament replacement into a wall of the tunnel to promote healing and bonding. In addition, the smooth shank provides a surface over which a replacement ligament can be positioned or looped if such a replacement ligament is used.
The pin of the present invention includes a head spaced apart from a threaded section of the pin so that the head of the pin engages the cortical bone of the femur and prevents the head from being counter sunk into the femur. This permits easy location of the pin through the skin should it be required to remove the pin. The pin of the present invention is easily removable from the femur when compared with the Kurosaka.TM. interference screw discussed above. As discussed above, access to the pin of the present invention can be obtained without substantial invasion of the knee.
According to one aspect of the present invention, a pin is provided for securing a replacement ligament inside a tunnel of a receptor bone. The pin includes a body portion having a threaded section for engaging the receptor bone to anchor the pin in the receptor bone. The body portion also includes means for engaging the replacement ligament to force the replacement ligament against a side wall of the tunnel to secure the replacement ligament inside a tunnel and to promote healing of the ligament. The pin further includes a head coupled to an end of the body portion adjacent the threaded section for driving the pin into the receptor bone.
In the illustrated embodiment, the engaging means includes a tapered shank located adjacent the threaded portion. The tapered shank is configured to enter a drilled hole having a predetermined diameter formed in the replacement ligament to force the replacement ligament against the wall of the tunnel. The tapered shank has a first diameter at a first end of the tapered shank opposite the threaded portion which is smaller than the predetermined diameter of the drilled hole. The tapered shank has a second diameter adjacent the threaded portion which is larger than the predetermined diameter so that the tapered shank engages the replacement ligament in the tunnel as the pin is inserted through the drilled hole in the replacement ligament to force the replacement ligament against a side wall of the tunnel to promote healing of the replacement ligament within the receptor bone.
Also in the illustrated embodiment, the pin includes a generally conical tip located on a opposite end of the body portion from the head. The generally conical tip is illustratively angled at an angle at about 30.degree..
The illustrated embodiment further includes a generally smooth neck located between the head and the threaded section of the body portion. The neck facilitates removal of the pin from the bone. The head is an external hex head to reduce the likelihood that the head will be buried in the receptor bone when the pin is installed into the receptor bone.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.